OpenAI moved GPT-5.5 Instant into the default ChatGPT slot on 5 May 2026 across all tiers. Reported benchmark gains are non-trivial — AIME 2025 jumps to 81.2 from 65.4, MMMU-Pro multimodal climbs to 76 from 69.2. The headline new feature is memory integration: the model now searches past conversations, uploaded files, and (with consent) Gmail to ground personalised answers. Enterprise security teams have flagged the Gmail hook as the dominant question on contract reviews this month.